US10695955B2 - Mold manufacturing method and anti-reflective film manufacturing method - Google Patents

Mold manufacturing method and anti-reflective film manufacturing method Download PDF

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US10695955B2
US10695955B2 US15/524,385 US201515524385A US10695955B2 US 10695955 B2 US10695955 B2 US 10695955B2 US 201515524385 A US201515524385 A US 201515524385A US 10695955 B2 US10695955 B2 US 10695955B2
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mold
attached object
height
work
predetermined height
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US20180281238A1 (en
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Nobuaki Yamada
Hidekazu Hayashi
Miho Yamada
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Sharp Corp
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Sharp Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/38—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/38—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
    • B29C33/3842—Manufacturing moulds, e.g. shaping the mould surface by machining
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/42—Moulds or cores; Details thereof or accessories therefor characterised by the shape of the moulding surface, e.g. ribs or grooves
    • B29C33/424—Moulding surfaces provided with means for marking or patterning
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/70—Maintenance
    • B29C33/72—Cleaning
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C37/00—Component parts, details, accessories or auxiliary operations, not covered by group B29C33/00 or B29C35/00
    • B29C37/0096—Trouble-shooting during starting or stopping moulding or shaping apparatus
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C59/00—Surface shaping of articles, e.g. embossing; Apparatus therefor
    • B29C59/02—Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/12—Anodising more than once, e.g. in different baths
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/18—After-treatment, e.g. pore-sealing
    • C25D11/24—Chemical after-treatment
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
    • G02B1/11—Anti-reflection coatings
    • G02B1/118—Anti-reflection coatings having sub-optical wavelength surface structures designed to provide an enhanced transmittance, e.g. moth-eye structures
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C59/00—Surface shaping of articles, e.g. embossing; Apparatus therefor
    • B29C59/02—Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing
    • B29C59/022—Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing characterised by the disposition or the configuration, e.g. dimensions, of the embossments or the shaping tools therefor
    • B29C2059/023—Microembossing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/38—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
    • B29C33/3814—Porous moulds
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/06—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used
    • C25D11/08—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used containing inorganic acids
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/06—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used
    • C25D11/10—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used containing organic acids

Definitions

  • the present invention relates to a mold manufacturing method and an antireflection film production method and, for example, to a method for manufacturing a mold whose surface has an inverted moth-eye structure and a method for producing an antireflection film with the use of the mold.
  • the “mold” includes molds that are for use in various processing methods (stamping and casting), and is sometimes referred to as a stamper.
  • the “mold” can also be used for printing (including nanoimprinting).
  • Display devices for use in TVs, cell phones, etc., and optical elements, such as camera lenses, etc. usually adopt an antireflection technique in order to reduce the surface reflection and increase the amount of light transmitted therethrough. This is because, when light is transmitted through the interface between media of different refractive indices, e.g., when light is incident on the interface between air and glass, the amount of transmitted light decreases due to, for example, Fresnel reflection, thus deteriorating the visibility.
  • the two-dimensional size of a raised portion of an uneven pattern which performs an antireflection function is not less than 10 nm and less than 500 nm.
  • the “two-dimensional size” of the raised portions refers to the area equivalent circle diameter of the raised portions viewed in a direction normal to the surface. For example, when the raised portions have a conical shape, the two-dimensional size of the raised portions is equivalent to the diameter of the base of the cone. The same applies to the “two-dimensional size” of the recessed portions.
  • This method utilizes the principles of a so-called moth-eye structure.
  • the refractive index for light that is incident on the substrate is continuously changed along the depth direction of the recessed portions or raised portions, from the refractive index of a medium on which the light is incident to the refractive index of the substrate, whereby, for example, reflection of the visible light band is prevented.
  • the moth-eye structure is advantageous in that it is capable of performing an antireflection function with small incident angle dependence over a wide wavelength band, as well as that it is applicable to a number of materials, and that an uneven pattern can be directly formed in a substrate. As such, a high-performance antireflection film (or antireflection surface) can be provided at a low cost.
  • the present applicant has developed a method of producing an antireflection film (or antireflection surface) which has a moth-eye structure with the use of an anodized porous alumina layer obtained by anodization of aluminum (Patent Documents 2 to 5).
  • Utilizing an anodized porous aluminum film can facilitate the manufacture of a mold which is used for formation of a moth-eye structure over a surface (hereinafter, “moth-eye mold”).
  • moth-eye mold a mold which is used for formation of a moth-eye structure over a surface
  • the structure of the surface of a moth-eye mold which is capable of forming a moth-eye structure is herein referred to as “inverted moth-eye structure”.
  • Patent Documents 1 to 5 are incorporated by reference in this specification.
  • Patent Document 1 Japanese PCT National Phase Laid-Open Publication No. 2001-517319
  • Patent Document 2 Japanese PCT National Phase Laid-Open Publication No. 2003-531962
  • Patent Document 3 Japanese Laid-Open Patent Publication No. 2009-166502
  • Patent Document 4 WO 2011/125486
  • Patent Document 5 WO 2013/183576
  • Patent Document 6 Japanese Laid-Open Patent Publication No. 2014-113710
  • Patent Document 7 Japanese Laid-Open Patent Publication No. 2014-71312
  • the present inventors produced antireflection films using a moth-eye mold and encountered such a problem that some of the antireflection films had defects ranging in size from 200 ⁇ m to 3 mm.
  • some of images viewed through the antireflection film were distorted. Details of this defect will be described later.
  • the present invention was conceived in order to solve the above-described problems.
  • the major objects of the present invention include providing a mold manufacturing method which is capable of improving the production yield of a film whose surface has a moth-eye structure and providing a method which is capable of efficiently producing such a film.
  • a mold manufacturing method of an embodiment of the present invention is a manufacturing method of a mold, the mold having at its surface a plurality of recessed portions whose two-dimensional size is not less than 10 nm and less than 500 nm when viewed in a direction normal to the surface, the method including: (a) providing a mold base which includes a metal base and an aluminum alloy layer formed on the metal base; (b) partially anodizing the aluminum alloy layer, thereby forming a porous alumina layer which has a plurality of minute recessed portions; (c) after step (b), bringing the porous alumina layer into contact with an etching solution, thereby enlarging the plurality of minute recessed portions of the porous alumina layer; (d) detecting a protrusion formed at a surface of the porous alumina layer or the mold base; (e) determining whether or not a height of the protrusion detected at step (d) is greater than a predetermined height; and (f) if it is determined at step
  • step (d) includes detecting a protrusion formed at the surface of the porous alumina layer, and step (d), step (e) and step (f) are performed after step (b) and step (c).
  • step (d) includes detecting a protrusion formed at the surface of the mold base, and step (d), step (e) and step (f) are performed before step (b) and step (c).
  • the predetermined height is not less than 3 ⁇ m and not more than 200 ⁇ m.
  • the predetermined height is not less than 10 ⁇ m and not more than 30 ⁇ m.
  • the mold base further includes an inorganic underlayer formed between the metal base and the aluminum alloy layer.
  • the mold manufacturing method further includes (g) after step (c), further performing anodization to grow the plurality of minute recessed portions.
  • step (b) and step (c) are further performed after step (g).
  • An antireflection film production method of an embodiment of the present invention includes: providing a mold manufactured by the mold manufacturing method as set forth in any of the above paragraphs; providing a work; irradiating a photocurable resin applied between the mold and a surface of the work with light, thereby curing the photocurable resin; and peeling the mold off from an antireflection film formed of the cured photocurable resin.
  • the photocurable resin is applied to the surface of the work, and a thickness of the photocurable resin applied to the surface of the work is equal to or greater than the predetermined height.
  • the thickness of the photocurable resin applied to the surface of the work is not less than 3 ⁇ m and not more than 200 ⁇ m.
  • the thickness of the photocurable resin applied to the surface of the work is not less than 10 ⁇ m and not more than 30 ⁇ m.
  • a mold can be manufactured which is capable of, for example, improving the production yield of a film whose surface has a moth-eye structure.
  • a method is provided which is capable of efficiently producing such a film.
  • FIG. 1( a ) to ( e ) are schematic cross-sectional views for illustrating a manufacturing method of a moth-eye mold 100 A of Embodiment 1 of the present invention.
  • FIG. 2( a ) to ( d ) are schematic cross-sectional views for illustrating a manufacturing method of the moth-eye mold 100 A of Embodiment 1 of the present invention.
  • FIG. 3( a ) to ( c ) are schematic cross-sectional views for illustrating a manufacturing method of a moth-eye mold 100 B of Embodiment 2 of the present invention.
  • FIG. 4( a ) is an image of a portion of the surface of a comparative example moth-eye mold 200 corresponding to a defect in an antireflection film, which was observed using a scanning electron microscope (SEM).
  • SEM scanning electron microscope
  • ( b ) is a SEM image of a cross section of the portion of the surface of the moth-eye mold 200 corresponding to the defect in the antireflection film.
  • ( c ) is a graph showing the result of a composition analysis of an attached object at an encircled portion of ( b ).
  • FIG. 5( a ) to ( c ) are schematic cross-sectional views for illustrating occurrence of a defect in an antireflection film which is produced using the comparative example moth-eye mold 200 .
  • FIG. 6 A graph in which the size w 210 of an attached object 210 on the surface of the comparative example moth-eye mold 200 is plotted against the height h 210 .
  • FIG. 4( a ) is a SEM image of a portion of the surface of the moth-eye mold 200 corresponding to a defect in an antireflection film, which was observed using a scanning electron microscope (SEM).
  • FIG. 4( b ) is a SEM image of a cross section of the portion of the surface of the moth-eye mold 200 corresponding to the defect in the antireflection film.
  • FIG. 4( c ) is a graph showing the result of a composition analysis of the attached object at an encircled portion of FIG. 4( b ) with the use of an energy-dispersive X-ray spectrometer (EDS).
  • EDS energy-dispersive X-ray spectrometer
  • the size of the attached object was several tens of micrometers ( ⁇ m).
  • the size of the attached object was about 60 ⁇ m.
  • the size of the attached object refers to the area equivalent circle diameter of the attached object viewed in a direction normal to the surface of the moth-eye mold.
  • a defect occurred over a range of several hundreds of micrometers ( ⁇ m) to several millimeters (mm), e.g., from 200 ⁇ m to 3 mm. Therefore, it was found that the size of the defect was several tens to several hundreds of times greater than the size of the attached object.
  • the following problem occurs due to the size of the defect in the antireflection film which is several tens to several hundreds of times greater than the size of the attached object on the surface of the moth-eye mold.
  • the moth-eye mold that has an attached object on the surface is used to produce an antireflection film, there is a probability that a defect occurs over a range of several hundreds of micrometers ( ⁇ m) to several millimeters (mm). The defect occurring over this range is perceived by an observer's eye and, thus, the antireflection film can be a defective product.
  • the size of the attached object is several tens of micrometers ( ⁇ m) and, thus, it is difficult to find the attached object by visual inspection across the surface of the moth-eye mold before production of the antireflection film. Therefore, it is difficult to suppress the decrease in the production yield of the antireflection film.
  • FIG. 5( a ) to FIG. 5( c ) are schematic cross-sectional views for illustrating occurrence of a defect in an antireflection film which is produced using the comparative example moth-eye mold 200 .
  • the moth-eye mold 200 and a work 42 which has a UV-curable resin 32 ′ over its surface are provided.
  • the moth-eye mold 200 has an inverted moth-eye structure over the surface.
  • the surface of the moth-eye mold 200 has one or a plurality of attached objects 210 .
  • the shape of the attached object 210 is, for example, generally spherical as shown in FIG. 5( a ) .
  • the shape of the attached object 210 can be generally spherical before the step of pressing the work 42 against the moth-eye mold 200 which will be described with reference to FIG. 5 ( b ).
  • the UV-curable resin 32 ′ is applied to, for example, the surface of the work 42 .
  • the UV-curable resin 32 ′ applied over the surface of the work 42 has a generally constant thickness h 32 ′.
  • the height h 210 of the attached object 210 is, for example, greater than the thickness h 32 ′ of the UV-curable resin 32 ′.
  • the height h 210 of the attached object 210 refers to a height in a direction normal to the surface of the moth-eye mold 200 .
  • the thickness h 32 ′ of the UV-curable resin 32 ′ refers to a thickness in a direction normal to the surface of the work 42 (or the moth-eye mold 200 ).
  • the size w 210 of the attached object 210 is, for example, 20 ⁇ m to 200 ⁇ m.
  • the work 42 which has the UV-curable resin 32 ′ over its surface is maintained pressed against the moth-eye mold 200 , and the UV-curable resin 32 ′ is irradiated with ultraviolet (UV) light such that the UV-curable resin 32 ′ is cured.
  • UV ultraviolet
  • the UV-curable resin 32 ′ since the height h 210 of the attached object 210 is greater than the thickness h 32 ′ of the UV-curable resin 32 ′ (see FIG. 5( a ) ), the UV-curable resin 32 ′ has a greater thickness in a region of the size w 32 d with the attached object 210 at its center than in the surrounding region.
  • the thickness h 32 ′ of the UV-curable resin 32 ′ see FIG.
  • the size w 32 d of the defect 32 d is several tens to several hundreds of times greater than the size w 210 of the attached object 210 .
  • the size w 32 d of the defect 32 d refers to the area equivalent circle diameter of the defect 32 d viewed in a direction normal to the antireflection film 32 .
  • a pinch roller 44 can be used to press the work 42 against the moth-eye mold 200 .
  • the UV-curable resin 32 ′ used can be, for example, an acrylic resin.
  • the work 42 may be, for example, a TAC (triacetyl cellulose) film.
  • the attached object 210 can have the shape of a deformed sphere.
  • the height h 210 of the attached object 210 can be smaller and the size w 210 of the attached object 210 can be greater than in the step illustrated in FIG. 5( a ) .
  • These variations have a tendency to increase as the height h 210 of the attached object 210 increases. Note that, however, also in the step illustrated in FIG. 5( b ) , the height h 210 of the attached object 210 is greater than the thickness h 32 ′ of the UV-curable resin 32 ′.
  • a crack sometimes appears in the surface of the attached object 210 as shown in FIG. 4( a ) .
  • the crack can be, for example, streaky in the surface of the attached object 210 .
  • bubbles 33 occur in the UV-curable resin 32 ′ around the attached object 210 .
  • the moth-eye mold 200 is separated (peeled off) from the work 42 , whereby a cured material layer (antireflection film) 32 to which the uneven structure of the moth-eye mold 200 (inverted moth-eye structure) is transferred is formed on the surface of the work 42 .
  • the defect 32 d occurs over the region of the size w 32 d .
  • the thickness of the film is greater than in the surrounding region.
  • the defect 32 d has, for example, a lens-like shape.
  • the thickness h 32 of the antireflection film 32 in a region surrounding the defect 32 d is generally equal to the thickness h 32 ′ of the UV-curable resin 32 ′ shown in FIG. 5( a ) .
  • defect used in this specification as for a film (e.g., antireflection film), such as the defect 32 d described above, includes a condition that a portion of the film has a greater thickness than its surrounding portion of the film.
  • a film which has such a defect is placed over the display surface of a display, for example, an image viewed through the defect portion can sometimes be distorted.
  • the present inventors carried out research concerning where in the manufacturing process of the moth-eye mold 200 the attached object 210 occurred.
  • the comparative example moth-eye mold 200 can be manufactured by a method disclosed in Patent Documents 2 to 5.
  • the method for manufacturing the comparative example moth-eye mold 200 includes the following steps, Step (A′) to Step (C′), as will be described later with reference to FIG. 1( a ) to FIG. 1( e ) .
  • the present inventors analyzed the constituents of the attached object 210 and found that, as seen from FIG. 4( c ) , aluminum (Al) is the major constituent, and the attached object 210 has the same constituents as those of the aluminum alloy layer 18 . Also, as seen from FIG. 4( b ) , the surface of the attached object 210 has a porous alumina layer which has an inverted moth-eye structure. It is estimated from these findings that the attached object 210 occurred after formation of the aluminum alloy layer 18 at the surface of the moth-eye mold 200 and before the anodization step (i.e., after Step (A′) and before Step (B′)).
  • the formation of the aluminum alloy layer 18 is carried out by, for example, sputtering in a chamber (vacuum chamber). It is estimated that, in the step of opening the chamber to the air for taking out a mold base from the chamber after an aluminum alloy is deposited to form the aluminum alloy layer 18 , a clod (particle) of the aluminum alloy in the chamber attaches to the surface of the aluminum alloy layer 18 , resulting in occurrence of the attached object 210 .
  • the attached object 210 occurring on the surface of the aluminum alloy layer 18 has the same composition as that of the aluminum alloy layer 18 and therefore has high adhesion to the aluminum alloy layer 18 .
  • the problem of difficulty in removing the attached object 210 arises. Even when the surface of the moth-eye mold 200 is washed before the anodization step, it is difficult to thoroughly remove the attached object 210 .
  • Step (A′) and Step (B′) the step of forming a porous alumina layer which has a thickness of, for example, about 0.1 ⁇ m to 0.3 ⁇ m and thereafter removing the formed porous alumina layer by etching may be performed between Step (A′) and Step (B′).
  • Step (A′) and Step (B′) the step of forming a porous alumina layer which has a thickness of, for example, about 0.1 ⁇ m to 0.3 ⁇ m and thereafter removing the formed porous alumina layer by etching.
  • FIG. 6 is a graph in which the size w 210 of the attached object 210 on the surface of the moth-eye mold 200 is plotted against the height h 210 .
  • the thickness h 32 ′ of the UV-curable resin 32 ′ was 6 ⁇ m, in each case, before the work 42 was pressed against the moth-eye mold 200 (see FIG. 5( a ) ). As seen from FIG. 6 , the height h 210 of the attached object 210 is not less than 6 ⁇ m in each case. It was thus verified that the height h 210 of the attached object 210 which can be the cause of the defect 32 d in the antireflection film 32 is equal to the thickness h 32 ′ of the UV-curable resin 32 ′ or greater than the thickness h 32 ′ of the UV-curable resin 32 ′.
  • the height h 210 of the attached objects 210 before the work 42 was pressed against the moth-eye mold 200 was greater than the measurements.
  • the height h 210 of the attached object 210 which can be the cause of the defect 32 d in the antireflection film 32 is greater than the thickness h 32 ′ of the UV-curable resin 32 ′.
  • a mold of the present embodiment is a mold which has over its surface a plurality of recessed portions whose two-dimensional size viewed in the normal direction of the surface is not less than 10 nm and less than 500 nm.
  • a mold of an embodiment of the present invention is a moth-eye mold which has, for example, an inverted moth-eye structure over its surface.
  • the moth-eye mold may be in the shape of a hollow cylinder or may be in the shape of a plate.
  • WO 2011/105206 of the present applicant, when a moth-eye mold in the shape of a hollow cylinder is used, the antireflection film can be efficiently produced according to a roll-to-roll method.
  • the entire disclosure of WO 2011/105206 is incorporated by reference in this specification. Note that the present invention is not limited to the embodiments which will be described in the following sections. In the drawings mentioned in the following sections, components which have substantially the same functions are designated by the same reference numerals, and the descriptions thereof are sometimes omitted.
  • a mold manufacturing method of Embodiment 1 of the present invention includes the following steps, Step (A) to Step (F).
  • the predetermined height in Step (E) and Step (F) is, for example, equal to the thickness h 32 ′ of the UV-curable resin 32 ′ (see FIG. 5( a ) ) applied to the work 42 .
  • Step (D), Step (E) and Step (F) are performed, for example, after Step (B) and Step (C).
  • an attached object which can be the cause of a defect in an antireflection film produced with the use of the mold can be selectively removed.
  • An attached object which can be the cause of a defect in an antireflection film can be removed before the antireflection film is produced with the use of the mold. The decrease in the production yield of the film produced with the use of the mold can be suppressed.
  • FIG. 1( a ) to FIG. 1( e ) and FIG. 2( a ) to FIG. 2( d ) are schematic cross-sectional views for illustrating a manufacturing method of a moth-eye mold 100 A of Embodiment 1 of the present invention.
  • FIG. 1( a ) to FIG. 1( e ) and FIG. 2( a ) to FIG. 2( d ) are schematic cross-sectional views for illustrating a manufacturing method of a moth-eye mold 100 A of Embodiment 1 of the present invention.
  • FIG. 1( e ) are schematic diagrams of a portion of the moth-eye mold 100 A which does not have an attached object 210 at its surface through the manufacturing process.
  • FIG. 2( a ) to FIG. 2( d ) are schematic diagrams of a portion of the moth-eye mold 100 A which has an attached object 210 at its surface through the manufacturing process.
  • a mold base 10 which includes a metal base 12 and an aluminum alloy layer 18 formed on the metal base 12 .
  • the surface 18 s of the mold base 10 has an attached object 210 .
  • the mold base 10 may further include an inorganic underlayer 16 between the metal base 12 and the aluminum alloy layer 18 .
  • the mold manufacturing method of Embodiment 1 may further include the step of forming the inorganic underlayer 16 on the metal base 12 after the step of providing the metal base 12 and before the step of forming the aluminum alloy layer 18 .
  • the metal base 12 used can be an aluminum base 12 whose aluminum purity is not less than 99.50 mass % and less than 99.99 mass % and which has relatively high rigidity.
  • the impurity contained in the aluminum base 12 may preferably include at least one element selected from the group consisting of iron (Fe), silicon (Si), copper (Cu), manganese (Mn), zinc (Zn), nickel (Ni), titanium (Ti), lead (Pb), tin (Sn) and magnesium (Mg). Particularly, Mg is preferred. Since the mechanism of formation of pits (hollows) in the etching step is a local cell reaction, the aluminum base 12 ideally does not contain any element which is nobler than aluminum.
  • the aluminum base 12 used contains, as the impurity element, Mg (standard electrode potential: ⁇ 2.36 V) which is a base metal. If the content of an element nobler than aluminum is 10 ppm or less, it can be said in terms of electrochemistry that the aluminum base 12 does not substantially contain the element.
  • Mg content is preferably 0.1 mass % or more of the whole. It is, more preferably, in the range of not more than about 3.0 mass %. If the Mg content is less than 0.1 mass %, sufficient rigidity cannot be obtained. On the other hand, as the Mg content increases, segregation of Mg is more likely to occur.
  • the content of the impurity element may be appropriately determined depending on the shape, thickness, and size of the aluminum base 12 , in view of required rigidity.
  • the appropriate Mg content is about 3.0 mass %.
  • the Mg content is preferably 2.0 mass % or less. If the Mg content exceeds 2.0 mass %, the extrudability deteriorates in general.
  • the aluminum base 12 used may be an aluminum pipe in the shape of a hollow cylinder which is made of, for example, JIS A1050, an Al—Mg based alloy (e.g., JIS A5052), or an Al—Mg—Si based alloy (e.g., JIS A6063).
  • the surface of the aluminum base 12 is preferably a surface cut with a bit. If, for example, abrasive particles are remaining on the surface of the aluminum base 12 , conduction will readily occur between the aluminum alloy layer 18 and the aluminum base 12 in a portion in which the abrasive particles are present. Not only in the portion in which the abrasive particles are remaining but also in a portion which has a roughened surface, conduction readily occurs between the aluminum alloy layer 18 and the aluminum base 12 . When conduction occurs locally between the aluminum alloy layer 18 and the aluminum base 12 , there is a probability that a local cell reaction will occur between an impurity in the aluminum base 12 and the aluminum alloy layer 18 .
  • the material of the inorganic underlayer 16 may be, for example, tantalum oxide (Ta 2 O 5 ) or silicon dioxide (SiO 2 ).
  • the inorganic underlayer 16 can be formed by, for example, sputtering.
  • the thickness of the tantalum oxide layer is, for example, 200 nm.
  • the thickness of the inorganic underlayer 16 is preferably not less than 100 nm and less than 500 nm. If the thickness of the inorganic underlayer 16 is less than 100 nm, there is a probability that a defect (typically, a void; i.e., a gap between crystal grains) occurs in the aluminum alloy layer 18 . If the thickness of the inorganic underlayer 16 is not less than 500 nm, insulation is likely to occur between the aluminum base 12 and the aluminum alloy layer 18 due to the surface condition of the aluminum base 12 . To realize anodization of the aluminum alloy layer 18 by supplying an electric current from the aluminum base 12 side to the aluminum alloy layer 18 , the electric current needs to flow between the aluminum base 12 and the aluminum alloy layer 18 .
  • a defect typically, a void; i.e., a gap between crystal grains
  • the aluminum alloy layer 18 can be anodized across the entire surface, while such a problem does not occur that supply of the electric current becomes more difficult as the anodization advances.
  • the aluminum alloy layer 18 can be anodized uniformly across the entire surface.
  • the film formation duration is increased, the surface temperature of the aluminum base 12 unnecessarily increases, and as a result, the film quality of the aluminum alloy layer 18 deteriorates, and a defect (typically, a void) occurs in some cases.
  • a defect typically, a void
  • the thickness of the inorganic underlayer 16 is less than 500 nm, occurrence of such a problem can be suppressed.
  • the aluminum alloy layer 18 is, for example, a film which is made of aluminum whose purity is not less than 99.99 mass % (hereinafter, sometimes referred to as “high-purity aluminum film”) as disclosed in Patent Document 4.
  • the aluminum alloy layer 18 is formed by, for example, vacuum deposition or sputtering.
  • the thickness of the aluminum alloy layer 18 is preferably in the range of not less than about 500 nm and not more than about 1500 nm. For example, the thickness of the aluminum alloy layer 18 is about 1 ⁇ m.
  • the aluminum alloy layer 18 may be an aluminum alloy film disclosed in Patent Document 5 in substitution for the high-purity aluminum film.
  • the aluminum alloy film disclosed in Patent Document 5 contains aluminum, a metal element other than aluminum, and nitrogen.
  • the “aluminum film” includes not only the high-purity aluminum film but also the aluminum alloy film disclosed in Patent Document 5.
  • the above-described aluminum alloy film enables to obtain a specular surface whose reflectance is not less than 80%.
  • the average grain diameter of crystal grains that form the aluminum alloy film when viewed in the normal direction of the aluminum alloy film is, for example, not more than 100 nm, and that the maximum surface roughness Rmax of the aluminum alloy film is not more than 60 nm.
  • the content of nitrogen in the aluminum alloy film is, for example, not less than 0.5 mass % and not more than 5.7 mass %.
  • the absolute value of the difference between the standard electrode potential of the metal element other than aluminum which is contained in the aluminum alloy film and the standard electrode potential of aluminum is not more than 0.64 V, and that the content of the metal element in the aluminum alloy film is not less than 1.0 mass % and not more than 1.9 mass %.
  • the metal element is, for example, Ti or Nd.
  • the metal element is not limited to these examples but may be such a different metal element that the absolute value of the difference between the standard electrode potential of the metal element and the standard electrode potential of aluminum is not more than 0.64 V (for example, Mn, Mg, Zr, V, and Pb). Further, the metal element may be Mo, Nb, or Hf.
  • the aluminum alloy film may contain two or more of these metal elements.
  • the aluminum alloy film is formed by, for example, a DC magnetron sputtering method.
  • the thickness of the aluminum alloy film is also preferably in the range of not less than about 500 nm and not more than about 1500 nm.
  • the thickness of the aluminum alloy film is about 1 ⁇ m.
  • a surface 18 s of the aluminum alloy layer 18 is anodized to form a porous alumina layer 14 which has a plurality of recessed portions (micropores) 14 p as shown in FIG. 1( b ) .
  • the porous alumina layer 14 includes a porous layer which has the recessed portions 14 p and a barrier layer (the base of the recessed portions (micropores) 14 p ).
  • the interval between adjacent recessed portions 14 p is approximately twice the thickness of the barrier layer and is approximately proportional to the voltage that is applied during the anodization. This relationship also applies to the final porous alumina layer 14 shown in FIG. 1( e ) .
  • the porous alumina layer 14 is formed by, for example, anodizing the surface 18 s in an acidic electrolytic solution.
  • the electrolytic solution used in the step of forming the porous alumina layer 14 is, for example, an aqueous solution which contains an acid selected from the group consisting of oxalic acid, tartaric acid, phosphoric acid, sulfuric acid, chromic acid, citric acid, and malic acid.
  • the surface 18 s of the aluminum alloy layer 18 is anodized with an applied voltage of 80 V for 55 seconds using an oxalic acid aqueous solution (concentration: 0.3 mass %, solution temperature: 10° C.), whereby the porous alumina layer 14 is formed.
  • the surface 210 s of the attached object 210 is also concurrently anodized, whereby a porous alumina layer 214 which has a plurality of recessed portions (not shown) is formed.
  • the plurality of recessed portions of the porous alumina layer 214 are not shown in FIG. 2( b ) to FIG. 2( d ) for the sake of simplicity but may be the same as the plurality of recessed portions 14 p of the porous alumina layer 14 .
  • There is a probability that the porous alumina layer 14 is not formed on a portion of the surface 18 s of the aluminum alloy layer 18 which is in contact with the attached object 210 .
  • the porous alumina layer 14 is brought into contact with an etchant such that a predetermined amount is etched away, whereby the opening of the recessed portions 14 p is enlarged as shown in FIG. 1( c ) .
  • the etching amount i.e., the size and depth of the recessed portions 14 p
  • the etching solution used may be, for example, an aqueous solution of 10 mass % phosphoric acid, organic acid such as formic acid, acetic acid or citric acid, or sulfuric acid, or a chromic/phosphoric acid solution.
  • the etching is performed for 20 minutes using a phosphoric acid aqueous solution (10 mass %, 30° C.).
  • the openings of the plurality of recessed portions of the porous alumina layer 214 formed on the surface 210 s of the attached object 210 are also concurrently enlarged as well as in the porous alumina layer 14 . Note that, however, it is estimated that the height h 210 and the size w 210 of the attached object 210 hardly change in the steps of anodizing and etching the surface 210 s of the attached object 210 .
  • the aluminum alloy layer 18 is again partially anodized such that the recessed portions 14 p are grown in the depth direction and the thickness of the porous alumina layer 14 is increased as shown in FIG. 1( d ) .
  • the growth of the recessed portions 14 p starts at the bottoms of the previously-formed recessed portions 14 p , and accordingly, the lateral surfaces of the recessed portions 14 p have stepped shapes.
  • the porous alumina layer 14 may be brought into contact with an alumina etchant to be further etched such that the pore diameter of the recessed portions 14 p is further increased.
  • the etching solution used in this step may preferably be the above-described etching solution. Practically, the same etching bath may be used.
  • the comparative example moth-eye mold 200 that includes the porous alumina layer 14 which has the inverted moth-eye structure is obtained as shown in FIG. 2( c ) .
  • a portion of the comparative example moth-eye mold 200 which does not have an attached object 210 at the surface may be the same as the moth-eye mold 100 A shown in FIG. 1( e ) . Since the process is ended with the anodization step, the recessed portions 14 p have pointed bottom portion. That is, the resultant mold enables formation of raised portions with pointed tip ends.
  • the porous alumina layer 14 (thickness: t p ) shown in FIG. 1( e ) includes a porous layer (whose thickness is equivalent to the depth D d of the recessed portions 14 p ) and a barrier layer (thickness: t h ). Since the porous alumina layer 14 has a structure obtained by inverting the moth-eye structure of the antireflection film 32 , corresponding parameters which define the dimensions may sometimes be designated by the same symbols.
  • the recessed portions 14 p of the porous alumina layer 14 may have, for example, a conical shape and may have a stepped lateral surface. It is preferred that the two-dimensional size of the recessed portions 14 p (the diameter of a circle equivalent to the area of the recessed portions 14 p when viewed in a normal direction of the surface), D p , is more than 20 nm and less than 500 nm, and the depth of the recessed portions 14 p , D d , is not less than 50 nm and less than 1000 nm (1 ⁇ m). It is also preferred that the bottom portion of the recessed portions 14 p is acute (with the deepest part of the bottom portion being pointed).
  • the recessed portions 14 p When the recessed portions 14 p are in a densely packed arrangement, assuming that the shape of the recessed portions 14 p when viewed in a normal direction of the porous alumina layer 14 is a circle, adjacent circles overlap each other, and a saddle portion is formed between adjacent ones of the recessed portions 14 p . Note that, when the generally-conical recessed portions 14 p adjoin one another so as to form saddle portions, the two-dimensional size of the recessed portions 14 p . D p , is equal to the adjoining distance D int .
  • the thickness of the porous alumina layer 14 , t p is not more than about 1 ⁇ m.
  • the aluminum remnant layer 18 r is part of the aluminum alloy layer 18 which has not been anodized.
  • the aluminum alloy layer 18 may be substantially thoroughly anodized such that the aluminum remnant layer 18 r is not present.
  • the inorganic underlayer 16 has a small thickness, it is possible to readily supply an electric current from the aluminum base 12 side.
  • the manufacturing method of the moth-eye mold illustrated herein enables manufacture of a mold which is for production of antireflection films disclosed in Patent Documents 2 to 5. Since an antireflection film used in a high-definition display panel is required to have high uniformity, selection of the material of the aluminum base, specular working of the aluminum base, and control of the purity and components of the aluminum film are preferably carried out as described above. Note that, however, a mold of an embodiment of the present invention is not limited to this example but is widely applicable to production of a film whose surface has a moth-eye structure. When producing a film which is not required to have high uniformity, the above-described mold manufacturing method can be simplified.
  • a mold in which the regularity of the arrangement of the recessed portions is low, and which is suitable to production of an antireflection film, can be manufactured.
  • a mold for formation of a moth-eye structure which has regularly-arranged raised portions can be manufactured, for example, as described in the following section.
  • the formed porous alumina layer is removed by etching, and then, anodization may be performed under the above-described conditions for formation of the porous alumina layer.
  • the porous alumina layer that has a thickness of 0.1 ⁇ m to 0.3 ⁇ m is realized by appropriately controlling the anodization duration.
  • the protrusion 210 includes the above-described attached object 210 .
  • the protrusion 210 and the attached object 210 are sometimes designated by the same reference numeral.
  • the protrusion 210 to be detected includes not only the attached object 210 but also, for example, an object which includes a component different from the attached object 210 (for example, organic matter, cellulose (e.g., including a TAC film), resin (e.g., including a UV-curable resin 32 ′ used for production of the antireflection film 32 ), etc.) and an object which is attributed to a cause different from that of the attached object 210 .
  • an object which includes a component different from the attached object 210 for example, organic matter, cellulose (e.g., including a TAC film), resin (e.g., including a UV-curable resin 32 ′ used for production of the antireflection film 32 ), etc.
  • an object which is attributed to a cause different from that of the attached object 210 for example, organic matter, cellulose (e.g., including a TAC film), resin (e.g., including a UV-curable resin 32 ′ used for production of the antireflection
  • Detection of the protrusion 210 includes obtaining information indicative of the position of the protrusion 210 on the moth-eye mold 200 .
  • the moth-eye mold is in the shape of a hollow cylinder, the position in the circumferential direction of the moth-eye mold and the position in a direction perpendicular to the base surface of the moth-eye mold are obtained.
  • a marker which specifies the position in the circumferential direction of the moth-eye mold can be used as the basis.
  • a protrusion (attached object) 210 whose shape is generally circular when viewed in a direction normal to the porous alumina layer 14 may be selected for detection.
  • the attached object 210 that can be the cause of a defect in the antireflection film is characteristic in its generally spherical so that it is possible to efficiently detect the protrusion 210 that can be the cause of a defect. Thus, it is possible to efficiently suppress occurrence of a defect in an antireflection film.
  • the predetermined height h th is equal to, for example, the thickness h 32 ′ of the UV-curable resin 32 ′ (see FIG. 5( a ) ) applied to the work 42 .
  • the predetermined height h th may be, for example, a smaller value than the thickness h 32 ′ of the UV-curable resin 32 ′ (see FIG. 5( a ) ) applied to the work 42 .
  • the predetermined height h th is not limited to this example but can be set to an arbitrary value.
  • the predetermined height h th is, for example, not less than 3 ⁇ m and not more than 200 ⁇ m.
  • the predetermined height h th is, for example, not less than 10 ⁇ m and not more than 30 ⁇ m.
  • the predetermined height h th is, for example, not more than 10 ⁇ m when the thickness h 32 ′ of the UV-curable resin 32 ′ (see FIG. 5( a ) ) applied to the work 42 is 10 ⁇ m.
  • the thickness h 32 ′ of the UV-curable resin 32 ′ (see FIG. 5( a ) ) applied to the work 42 can also be determined according to the value of the predetermined height h th .
  • the UV-curable resin 32 ′ is applied to, for example, the surface of the work 42 .
  • the thickness h 32 ′ of the UV-curable resin 32 ′ applied to the work 42 has, for example, a value which is equal to the predetermined height h th or a value which is greater than the predetermined height h th .
  • the thickness h 32 ′ of the UV-curable resin 32 ′ applied to the work 42 is, for example, not less than 3 ⁇ m and not more than 200 ⁇ m.
  • the thickness h 32 ′ of the UV-curable resin 32 ′ applied to the work 42 is, for example, not less than 10 ⁇ m and not more than 30 ⁇ m.
  • the predetermined height h th is less than 3 ⁇ m, a large number of protrusions (attached objects) 210 are subjected to laser irradiation, so that the time and/or cost required for the laser light irradiation step increase.
  • the predetermined height h th is preferably not less than 3 ⁇ m.
  • the accuracy of the determination step can improve. That is, the probability of failing to detect a protrusion (attached object) 210 which is greater than the predetermined height h th decreases. As a result, the efficiency of detection of the protrusion 210 that can be the cause of a defect can improve.
  • the thickness h 32 ′ of the UV-curable resin 32 ′ applied to the work 42 can be increased by, for example, using a UV-curable resin 32 ′ which has a high viscosity. If the viscosity of the UV-curable resin 32 ′ is high, there is a probability that the UV-curable resin 32 ′ is less likely to fill the recesses of the inverted moth-eye structure at the surface of the moth-eye mold 200 and, as a result, the antireflection function of a produced antireflection film is disadvantageously suppressed.
  • the produced antireflection film 32 is soft so that there is a probability that either or both of the following problems arise: the antireflection film 32 is likely to deform; and scratches are likely to be formed in the antireflection film 32 .
  • the thickness h 32 ′ of the UV-curable resin 32 ′ (see FIG. 5( a ) ) applied to the work 42 is preferably not more than 200 ⁇ m. More preferably, the thickness h 32 ′ of the UV-curable resin 32 ′ (see FIG. 5( a ) ) applied to the work 42 is, for example, not more than 30 ⁇ m.
  • the viscosity of the UV-curable resin 32 ′ can be increased by, for example, increasing the concentration of monomers in the UV-curable resin 32 ′.
  • the UV-curable resin 32 ′ includes, for example, a solvent in which monomers are dissolved.
  • the UV-curable resin 32 ′ can further include a photopolymerization initiator.
  • the UV-curable resin 32 ′ may further include, for example, oligomers.
  • the UV-curable resin 32 ′ includes oligomers in addition to monomers, the UV-curable resin 32 ′ can be prevented from decreasing the volume of the antireflection film 32 in production of the antireflection film 32 by curing, and/or the produced antireflection film 32 can be prevented from becoming hard.
  • the UV-curable resin 32 ′ may further include a lubricant (for example, including fluoric lubricants, silicone lubricants, etc.).
  • the determination may be performed by, for example, directly or indirectly measuring the height h 210 of each attached object 210 with the use of a microscope and comparing measurements with the value of the predetermined height h th .
  • a laser scanning microscope may be used.
  • a confocal laser scanning microscope is capable of brightly imaging only a focused portion and, due to this characteristic, an image of high resolution can be obtained.
  • the measurement is combined with scanning in the vertical direction (Z-axis direction), the height can be accurately measured.
  • the protrusion 210 is irradiated with laser light such that the height of the protrusion 210 is lower than the predetermined height h th .
  • the protrusion (attached object) 210 at least partially evaporates or sublimes so that its height h 210 decreases.
  • the laser light includes, for example, ultraviolet light, visible light and infrared light.
  • a known laser for example, such as a solid-state laser (e.g., YAG laser and the like) or a gas laser (e.g., excimer laser, CO 2 laser) can be used.
  • a protrusion 210 which is determined to have a height h 210 greater than the predetermined height h th is selectively irradiated with the laser light.
  • the amount of the laser light can be appropriately set depending on the size of the protrusion 210 and other factors. For example, when a pulsed laser such as a YAG laser is used, the pulse width and the number of irradiations can be modified. When the area irradiated with the laser light is smaller than the protrusion 210 , the laser light may be moved relative to the protrusion 210 such that the protrusion 210 is irradiated with the laser light.
  • the protrusion 210 is irradiated with the laser light, it is determined whether or not the height h 210 of the protrusion 210 is greater than the predetermined height h th . If it is determined that the height h 210 of the protrusion 210 is greater than the predetermined height h th , the protrusion 210 is again irradiated with the laser light. These steps may be repeated till it is determined that the height h 210 of the protrusion 210 is not more than the predetermined height h th .
  • the irradiation may be performed with varying irradiation areas and/or varying irradiation intensities.
  • the irradiation may be performed in such a manner that the first irradiation is performed with the largest irradiation area while the final irradiation is performed with the smallest irradiation area.
  • the irradiation may be performed in such a manner that the first irradiation is performed with the highest irradiation intensity while the final irradiation is performed with the lowest irradiation intensity.
  • the protrusion 210 may be substantially thoroughly removed such that a portion of the surface of the moth-eye mold 200 from which the protrusion 210 has been removed has a recess.
  • the above-described detection step, determination step and laser light irradiation step may be performed on each of the protrusions 210 , i.e., these steps may be repeated as many as the number of the protrusions 210 .
  • the detection step, determination step and laser light irradiation step may be performed only once, simultaneously on all of a plurality of protrusions 210 .
  • the detection step may be performed in such a manner that the surface of the moth-eye mold 200 is imaged by a camera, or the like, via a microscope, and protrusions 210 are automatically detected based on the resultant image.
  • the moth-eye mold 100 A shown in FIG. 1( e ) and FIG. 2( d ) is obtained.
  • Patent Document 6 and Patent Document 7 mentioned above disclose mold repairing methods.
  • the mold repairing method of Patent Document 6 includes the foreign object detection step of detecting a foreign object adhering to the surface of a mold and the foreign object removal step of removing the foreign object detected in the foreign object detection step by laser irradiation.
  • Patent Document 6 describes using an atomic-force microscope (AFM) or a scanning electron microscope (SEM) for detection of foreign objects in the mold repairing method of Patent Document 6.
  • the mold repairing method of Patent Document 7 includes the step of filling a defective portion with a repair agent, the step of pressing a repair die against the repair agent, and the step of curing the repair agent by ultraviolet irradiation.
  • the mold repairing method of Patent Document 6 does not intend to selectively remove an attached object which can be the cause of a defect in an antireflection film.
  • the mold repairing method of Patent Document 7 intends to repair a defective portion in the shape of a recess and is not capable of removing an attached object which can be the cause of a defect in an antireflection film.
  • an attached object which can be the cause of a defect in an antireflection film produced with the use of a mold can be selectively removed. Also, before an antireflection film is produced with the use of a mold, an attached object which can be the cause of a defect in the antireflection film can be removed in advance. The decrease in the production yield of the film produced with the use of the mold can be efficiently suppressed.
  • an antireflection film is produced at part of the surface of a work (e.g., TAC film).
  • the work has a length of, for example, about 3000 m to about 4000 m and is wound around a winding roller.
  • An antireflection film is produced at the surface of part of the work which has a length of, for example, about 20 in to about 30 m.
  • the work is pulled out from the winding roller. After the antireflection film is produced at the surface, the work is wound up by another winding roller.
  • the repairing of the moth-eye mold needs to be performed only on the portion specified from the produced film and, therefore, an increase in time and/or procedure required for the repairing step can be suppressed. Also, the influence by the repairing (e.g., laser irradiation) on the surface of the moth-eye mold (e.g., the inverted moth-eye structure) can be suppressed.
  • an antireflection film is produced at the surface of the remaining part of the work. Since the repairing of the moth-eye mold has been performed, occurrence of a defect in the antireflection film produced at the surface of the remaining part of the work is suppressed.
  • the antireflection film production method and mold repairing method there is a probability that an antireflection film produced before the repairing of the moth-eye mold has a defect and, therefore, there is a probability that the production yield of the antireflection film disadvantageously decreases. Also, according to the above-described method, after an antireflection film is formed at the surface of part of the work, inspection of the surface of the antireflection film and repairing of the moth-eye mold are performed, and thereafter, an antireflection film is again produced at the surface of the remaining part of the work. In such a production process, there is a probability that the time and/or procedure disadvantageously increase.
  • an attached object which can be the cause of a defect in an antireflection film is removed in advance before the antireflection film is produced with the use of a mold, occurrence of the two problems described above can be suppressed. It is estimated that, from the viewpoint of suppressing occurrence of the two problems described above, removing an attached object which can be the cause of a defect in an antireflection film in advance is more effective when the number of attached objects to be removed in advance is small. According to a mold manufacturing method of an embodiment of the present invention, as previously described, an attached object which can be the cause of a defect in an antireflection film can be removed in advance before the antireflection film is produced with the use of a mold.
  • each of the moth-eye molds one attached object (protrusion) 210 was detected, and the height h 210 of the detected attached object 210 was measured.
  • the measurement of the height h 210 was carried out using a confocal microscope (hybrid laser microscope OPTELICS (registered trademark) HYBRID standard model L3 manufactured by Lasertec Corporation).
  • the determination step was performed by comparing the height h 210 of the attached object 210 with the predetermined height h th .
  • the predetermined height h th was 6 ⁇ m. This is equal to the thickness h 32 ′ of the UV-curable resin 32 ′ applied to the work 42 .
  • Antireflection films were produced using the respective moth-eye molds before laser light irradiation. It was verified that a defect occurs in the antireflection films due to the attached object 210 which is higher than the predetermined height h th .
  • the height h 210 of the attached object 210 was greater than the predetermined height h th and, therefore, the attached object 210 was irradiated with laser light.
  • the laser light was YAG laser (wavelength: 532 nm, pulse width: 6 ns).
  • the laser oscillator used was HSL-5000II FS (manufactured by HOYA CANDEO OPTRONICS).
  • the irradiation power of the laser light was 450 mJ.
  • the beam shape of the laser light used for irradiation was a generally square shape of about 30 ⁇ m on each side.
  • Example 1a and Example 1b the attached object 210 was irradiated with the laser light about 30 to 50 times till the height h 210 of the attached object 210 became smaller than the predetermined height h th (6 ⁇ m). The irradiation with the laser light was performed while the position to be irradiated with the laser light was appropriately varied in accordance with the attached object 210 .
  • a correspondence table was created beforehand using test samples. For the difference between the height h 210 of the attached object 210 and the predetermined height h th , the number of irradiations with the laser light was determined according to the correspondence table. After the attached object 210 was irradiated with the laser light based on the determined number of irradiations, the height h 210 of the attached object 210 was measured, and the irradiation with the laser light was further repeated till the height h 210 of the attached object 210 reached the predetermined value.
  • Comparative Example 1 the irradiation with the laser light was stopped when the height h 210 of the attached object 210 reached 8 ⁇ m, which was a value greater than the predetermined height h th (6 ⁇ m).
  • Antireflection films were produced using the respective moth-eye molds after being irradiated with the laser light. In Example 1a and Example 1b, the antireflection films had no defect. In Comparative Example 1, the antireflection film had a defect.
  • the mold manufacturing method of Embodiment 2 of the present invention is different from the mold manufacturing method of Embodiment 1 in that the detection step, the determination step and the laser light irradiation step are performed before the anodization step and the etching step.
  • the detection step is the step of detecting a protrusion formed at the surface of the mold base.
  • the mold base refers to an object of the anodization and the etching in the mold manufacturing process.
  • the mold manufacturing method of Embodiment 2 of the present invention may be the same as the mold manufacturing method of Embodiment 1 except that the detection step, the determination step and the laser light irradiation step are performed before the anodization step and the etching step.
  • an attached object which can be the cause of a defect in an antireflection film produced with the use of a mold can be selectively removed. Also, an attached object which can be the cause of a defect in an antireflection film can be removed in advance before the antireflection film is formed with the use of a mold. The decrease in the production yield of the film produced with the use of a mold can be suppressed.
  • Embodiment 2 of the present invention before a porous alumina layer which has a plurality of recessed portions is formed, an attached object on the mold base is irradiated with laser light. Therefore, the influence of the laser light irradiation on the plurality of recessed portions can be reduced.
  • FIGS. 3( a ) to 3( c ) are schematic cross-sectional views for illustrating a manufacturing method of the moth-eye mold 100 B of Embodiment 2 of the present invention.
  • FIGS. 3( a ) to 3 ( c ) are cross-sectional views of part of the moth-eye mold 100 B in which an attached object 210 is present on the surface in the manufacturing process.
  • a mold base 10 shown in FIG. 1( a ) and FIG. 3( a ) is provided.
  • the protrusion 210 is irradiated with laser light such that the height h 210 of the protrusion 210 becomes smaller than the predetermined height h th as shown in FIG. 3( b ) .
  • the anodization step and the etching step are performed as shown in FIGS. 1( b ) to 1( e ) and FIG. 3( c ) .
  • the surface 210 s of the attached object 210 is also anodized concurrently, so that a porous alumina layer 214 which has a plurality of recessed portions (not shown) is formed as shown in FIG. 3( c ) .
  • the plurality of recessed portions of the porous alumina layer 214 which are not shown in FIG.
  • 3( c ) for the sake of simplicity, may be the same as the plurality of recessed portions 14 p of the porous alumina layer 14 .
  • the porous alumina layer 14 is not formed on part of the surface 18 s of the aluminum alloy layer 18 which is in contact with the attached object 210 .
  • the moth-eye mold 100 B shown in FIG. 3( c ) is obtained.
  • the cross-sectional view of part of the moth-eye mold 100 B which does not have the attached object 210 at the surface is the same as that of the moth-eye mold 100 A shown in FIG. 1( e ) .
  • an antireflection film has been described as an example of the film whose surface has a moth-eye structure.
  • a mold of an embodiment of the present invention is not limited to this example but is widely applicable to production of a film whose surface has a moth-eye structure.
  • a film production method of an embodiment of the present invention is not limited to antireflection films but is widely applicable to production of a film whose surface has a moth-eye structure.
  • a mold of an embodiment of the present invention can be used for transfer in a wide variety of nanoimprinting techniques.
  • a mold of an embodiment of the present invention is not limited to this example but is widely applicable to a mold for formation of, for example, raised portions with non-pointed tip ends (e.g., nanopillars). That is, the shape of micro recessed portions at the surface of a mold of an embodiment of the present invention is not limited to a generally conical shape but may be, for example, a generally circular truncated cone or may be a generally cylindrical shape.
  • the bottom of the micro recessed portions is not limited to a pointed bottom but may be, for example, rounded or may be planar.
  • the shape of the opening of the micro recessed portions is not limited to a circular shape but may be rectangular, for example.
  • the plurality of micro recessed portions may be arranged regularly or may be arranged irregularly (randomly).
  • a mold of the present invention can be used in production of an antireflection film (antireflection surface) or the like.

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  • General Physics & Mathematics (AREA)
  • General Chemical & Material Sciences (AREA)
  • Surface Treatment Of Optical Elements (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)
  • Shaping Of Tube Ends By Bending Or Straightening (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
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JP7470736B2 (ja) 2022-05-17 2024-04-18 ジオマテック株式会社 食品付着防止表面を備える物品、食品付着防止表面の形成方法

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CN107148335A (zh) 2017-09-08
WO2016072362A1 (ja) 2016-05-12

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